Magnetic sensors may be subject to saturation at high magnetic field strengths. Such saturation may cause non-linearity in the response of the sensor, and may even lead to a reversal of sensitivity, so that an increase in the field above saturation reduces the magnitude of the output of the sensor, rather than increasing it.
Magnetic sensors comprising anisotropic magnetoresistive (AMR) elements tend to become non-linear in response to a field that is above a saturation threshold. This non-linearity causes a distortion of the output signal. AMR based speed sensors are a specific type of magnetic sensor, which may be provided with a permanent magnet, producing a bias field. Such sensors tend to be required to respond to an external magnetic field in a specific direction, associated with an adjacent encoder wheel. The external magnetic field may be associated with teeth or permanent magnets of an encoder wheel. AMR speed sensors are typically required to be able to respond to a wide dynamic range of such an external magnetic field. At one end of the scale, high sensitivity is required to identify small external fields, and at the other end, saturation of the sensor can lead to problems due to distortion of the signal arising from non-linearity.
A solution that overcomes or ameliorates at least some of the above mentioned problems is desired.